This disclosure is generally directed to pigment dispersions, particularly pigment dispersions for use in curable phase change inks, curable phase change inks utilizing the pigment dispersions, and a method of evaluating the suitability of a pigment dispersion for use in a curable phase change ink.
Pigment dispersions required for curable phase change inks must meet certain requirements to enable the preparation of filterable and stable inks. These criteria include filtration of the curable phase change inks made using the pigment dispersion through small pore sized filters, and stability at elevated temperatures over extended time periods, for example weeks.
Pigment dispersions that meet the requirements are still desired, particularly dispersions using a dispersant that is able to form pigment dispersions meeting the requirements when used with differently colored pigments, for example when used with cyan, yellow, magenta and black pigments. In this way, an ink set comprised of curable phase change inks for the full color gamut, for example having the colors cyan, yellow, magenta an black, may be prepared in which all of the colored inks of the ink set use an identical pigment dispersion, desirably in the same amount. The advantage of such an ink set is that the colored curable phase change inks of the ink set can be readily mixed without issue to form spot or custom colors. Co-pending application Ser. No. 12/946,527, entitled “Ink Set And Manufacturing Process For Phase Change Inks,” and incorporated herein by reference in its entirety, is directed to such curable phase change ink sets.
Prior to the present application, there were very few pigment/dispersant combinations that met the criteria for pigment dispersions to be used in curable phase change inks, and no dispersants used to prepare pigment dispersions for differently colored pigments such that an ink set as described above may be prepared. In particular, cyan pigment dispersions that yield stable and filterable curable phase change inks have not been known.